If the mean and the variance of a binomial variate X are 1 and 0.75 respectively, then which of the following is true?

A box contains 8 red and N green balls. Two balls are drawn at random from it. If X is the random variable representing the number of green balls drawn and $E(X) = 1.2$, then $N = \ldots$

Resultant of two vectors $\vec{P}$ and $\vec{Q}$ is of magnitude A. If $\vec{Q}$ is reversed, then the resultant is of magnitude B. The value of $A^2 + B^2$ is

Mass and volume of a body are found to be $(6.00 \pm 0.03)$ kg and $(2.00 \pm 0.02)$ $\text{m}^3$ respectively. Then the density of a body is